Rotary hook for sewing machines



Nov. 2, 1965 L. J. KUHAR 3,215,105

ROTARY HOOK FOR SEWING MACHINES Filed Sept. 9, 1963 Fig. 3

INVENTOR.

WITNESS Ludwig J. Kuhur BY fla -Q34 "Bk (3 in! X TTORNEY United StatesPatent 3,215,105 ROTARY HOOK FOR SEWING MACHINES Ludwig J. Kuhar, Clark,N.J., assignor to The Singer Company, New York, N.Y., a corporation ofNew Jersey Filed Sept. 9, 1963, Ser. No. 307,684 Claims. (Cl. 112-228)This invention relates to rotary hooks for sewing machines and moreparticularly to an improved needle guard for such rotary hooks.

This invention is a further development of the invention forming thesubject matter of the copending United States application of KettererSerial No. 169,412 filed January 29, 1962 now Patent No. 3,120,204. Thatinvention, as well as the one of the present application provide, interalia, improved needle guards for rotary hooks.

When a rotary hook is secured to the hook shaft of a sewing machine, itmust be adjusted so that its loop seizing beak will engage the needlethread loop when the needle is in a particular position. This adjustmentis usually made by changing the angular relationship of the rotary hookand the shaft. As the needle guard is fastened to the hook, thisadjustment unfortunately causes the needle guard to change its positionrelatively to the needle. It is desirable that the needle guard be sosecured to the hook that it may be accurately adjusted relatively to theneedle irrespective to the relative position of the rotary hook and hookshaft.

The importance of the needle guard adjustment can be understood from thefact that when seizure by the rotary hook of the thread-loop presentedby the needle takes place, the needle has started its upstroke and thusthe needle is moving vertically in a direction away from the rotaryhook. By necessity, the needle guard at loop seiz ing time is locatedvertically below the loop-seizing beak on the rotary hook and guards theneedle through contact with it below the eye of the needle and very nearthe upper end of the taper of the needle. The taper of the many types ofneedles used in sewing machines has different configurations dependingupon the material being stitched (leather, cloth, etc.). The presence ofthe different tapers and different diameter needles, coupled with thefact that when maximum needle guarding is necessary the needle is movingin a direction away from the hook, makes it very desirable to provide aneedle guard having capacity whereby it can be very accurately adjustedto function with the desired rotary hook timing and with the particularneedle chosen for the material to be stitched.

It is therefore an object of this invention to provide a rotary hookwith a needle guard which is adjustable both axially of andcircumferentially about the hook shaft thereby to accommodate needles ofvarious sizes and permit positioning the needle guard with respect tothe loop seizing beak.

Other objects and purposes of this invention, will be evident from thefollowing description, claims and drawings which describe and illustrateone embodiment of the present invention.

In the drawings:

FIG. 1 is a fragmentary perspective view of a sewing machine rotary hookembodying the present invention.

FIG. 2 is a top plan view of the rotary hook shown in FIG. 1.

FIG. 3 is a fragmentary elevational view, partly in section, of therotary hook and thread carrying needle, showing the hook beak in loopseizing position.

With further reference to the drawings, there is illustrated a sewingmachine throat plate 1 which has a needle aperture 2 through which aneedle 3 reciprocates. A needle thread T is threaded through the eye 4of the needle 3. Beneath the throat plate 1 is a hook shaft 5 on3,215,105 Patented Nov. 2, 1965 which is mounted a rotary hook,indicated generally at 6, which cooperates with the needle 3 to formlock stitches. The hook 6, which is generally of conventionalconfiguration includes a cup shaped hook body 7 and a hub 8 that issecured by set screw 9 to the shaft 5. The hook body 7 is formed with aloop seizing beak 10 that terminates in a loop seizing point 11. Uponrotation of the hook shaft, the hook 6 is rotated about the axis of theshaft 5 and the loop seizing point 11 moves in a circular path of traveldefining a plane normal to the axis of the hook shaft 5. The needle 3defines a needle path relatively to the hook 6 and the hook 6 isarranged to one side of and closely adjacent to the plane defined by thepath of travel of the loop seizing point 11.

Within the hook body 7 is journaled a bobbin carrier 14, which is heldin the hook body by a gib 15 secured by screws 16 to the periphery ofthe hook body 7. The bobbin carrier 14 is held against rotation with thehook body 7 by a rotation restraining finger 17. A thread guard 18 issecured to the periphery of the hook body 7 by screws 19.

The gib 15 has a flange 20 which is spaced from the plane defined by thepath of travel of the loop seizing point 11 and disposed on the side ofthe plane opposite from the needle 3. This spacing is to provideclearance for the needle 3 as it descends into cooperation with thehook. After reaching its point of maximum penetration, the needle beginsto rise, and as it does, it throws a loop of thread which is thenentered by the loop seizing point 11. To insure loop seizure, the point11 must pass immediately adjacent to the needle 3. However the needlemay be bent or may be deflected so that, during operation, it may bepositioned in the path of travel of the point 11 and thus struck by it,in which case it would of course become further bent or broken and alsomay damage the point 11. To avoid this, a needle guard 25 is providedwhich is adapted to engage the needle 3 during the time when the point11 is passing adjacent to the needle 3 at a point immediately below theeye 4 and to position the needle closely adjacent to but out of the pathof travel of the point 11.

The needle guard adjustment-means include a support element 26 which hasa flat portion 27 in which is an elongated aperture 28 disposedsubstantially parallel to the hook shaft 5. Extending through theaperture 28 and threadedly engaged in the hub 8 is a screw 29 whichsecures the support element 26 to the hook 6. The screw 29 may beloosened so as to permit the support element to be moved in a directionperpendicular to the plane defined by the path of point 11 or, in otherwords, in a direction axially of the hook shaft 5.

The support element 26 has a raised portion 30 on which is a tongue 31and mounted on the support element is the needle guard 25. The needleguard 25 has a block portion 33 which has a slot or groove 34 in itsbottom. The tongue 31 is fitted within the groove 34 when the needleguard 25 is mounted on the support element 26. The needle guard 25 issecured to the support element 26 by screws 35 which extend through anelongated aperture 36 which is substantially perpendicular to theaperture 28. The support element 26 is limited in one direction of itsadjustment relatively to the hook by the side 38 of the block portion 33engaging the rearmost wall 39 of the hook body 7.

The needle guard 25 has a concaved surface 40 which provides clearancepermitting the usual needle thread loop to be formed. At the end of theconcaved surface 40 there is formed a needle positioning surface 41. Sothat no appreciable impact may be imparted to the back limb of theneedle thread loop by the needle guard, the gib 15 is provided with athread deflecting surface 42.

A loop controlling tail 45 is made integral with the needle guard 25 tocontrol the thread-loop as it is withdrawn from the hook and the angleof the tail 45 is made obtuse to encourage the thread loop off the tailon needle guard.

When making the previously mentioned adjustment so as to accommodateneedles of various sizes the screw 29 is loosened sufliciently to allowthe support element 26 and associated needle guard 25 to be moved towardand away from the needle path. When the adjustment is satisfactorilymade, the screw 29 is tightened to secure the needle guard with thehook.

When making the previously mentioned adjustment which causes the needlepositioning surface 91 to engage the needle at the proper point in itsstroke and at the time the loop seizing beak is passing the needle 11,screws 35 are loosened sufiiciently to allow the needle guard to bemoved in a direction perpendicular to the needle path. When theadjustment is satisfactorily made, the screws 35 are then tightened tosecure the needle guard with the hook.

Having thus described the nature of this invention, what I claim hereinis:

1. In a rotary hook for sewing machines a hook body, a loop seizing beaksecured thereto for rotation therewith and including a loop seizingpoint which point has a circular path of travel defining a plane normalto the axis of rotation of said hook body, a needle guard secured withsaid hook body for rotation therewith and including a needle positioningsurface .for engaging a needle and positioning it relatively to saidloop seizing point and means permitting adjustment of said needle guardin a direction perpendicular to said plane.

2. In a rotary hook for sewing machines a hook body, a loop seizing beaksecured thereto for rotation therewith and including a loop seizingpoint which point has a circular path of travel defining a plane normalto the axis of rotation of said hook body, a needle guard secured withsaid hook for rotation therewith and including a needle positioningsurface for engaging a needle and positioning it relatively to said loopseizing point and fastening means for securing said needle guard withsaid hook, said fastening means including means for adjusting saidneedle guard in a direction parallel to said plane.

3. The invention as defined in claim 2 and including means permittingadjustment of said needle guard in a direction perpendicular to saidplane.

4. In a rotary hook for sewing machines a hook body, a loop seizing beaksecured thereto for rotation therewith and including a loop seizingpoint which point has a circular path of travel defining a plane normalto the axis of rotation of said hook body, a needle guard secured withsaid hook body for rotation therewith and including a needle positioningsurface for engaging a needle and positioning it relative to said loopseizing point, a support element, said needle guard being adjustablysecured to said element and said element being adjustably secured tosaid hook.

5. A loop taker for a sewing machine including a loop seizing point, aneedle guard having a needle positioning surface, fastening means forsecuring said needle guard on said loop taker with said needlepositioning surface disposed adjacent said loop seizing point, saidfastening means including means for adjusting said needle positioningsurface relatively to said loop taker and said loop seizing point.

References Cited by the Examiner UNITED STATES PATENTS 2,019,284 10/35Wesson 112-228' JORDAN FRANKLIN, Primary Examiner.

1. IN A ROTARY HOOK FOR SEWING MACHINES A HOOK BODY, A LOOP SEIZING BEAKSECURED THERETO FOR ROTATION THEREWITH AND INCLUDING A LOOP SEIZINGPOINT WHICH POINT HAS A CIRCULAR PATH OF TRAVEL DEFINING A PLANE NORMALTO THE AXIS OF ROTATION OF SAID HOOK BODY, A NEEDLE GUARD SECURED WITHSAID HOOK BODY FOR ROTATION THEREWITH AND INCLUDING A NEEDLE POSITIONINGSURFACE FOR ENGAGIONG A NEEDLE AND POSITIONING IT RELATIVELY TO SAIDLOOP SEIZING POING AND MEANS PERMITTING ADJUSTMENT OF SAID NEEDLE GUARDIN A DIRECTION PERPENDICULAR TO SAID PLANE.